diff -Nru a/driver/prefsw.c b/driver/prefsw.c
--- a/driver/prefsw.c	2021-02-19 02:52:32.000000000 +0100
+++ b/driver/prefsw.c	2021-05-07 15:20:09.280321274 +0200
@@ -798,7 +798,10 @@
 	     sure that the bits actually land on the disk right away. */
           /* Update 2020: Apparently here in the future, this sometimes takes
              3+ seconds, so let's not. */
+/* Interix has no sync() or alike. */
+#ifndef __INTERIX
 	  /* sync(); */
+#endif
 
           status = 0;    /* wrote and renamed successfully! */
 	}
diff -Nru a/driver/setuid.c b/driver/setuid.c
--- a/driver/setuid.c	2021-02-05 16:16:23.000000000 +0100
+++ b/driver/setuid.c	2021-05-07 15:21:05.987949943 +0200
@@ -104,9 +104,12 @@
   if (uid == (uid_t) -1) uid = (uid_t) -2;
 
   errno = 0;
+  
+#ifndef __INTERIX
   if (setgroups_needed_p (gid) &&
       setgroups (1, &gid) < 0)
     sgs_errno = errno ? errno : -1;
+#endif
 
   errno = 0;
   if (setgid (gid) != 0)